Explore the progress made in combating citrus greening by the USDA Scion Breeding Program

In our latest column in Central Florida Ag News, we looked at the information shared in a presentation from the 2020 Florida Citrus Show: “Progress of the USDA Scion Breeding Program.” The presentation was given by USDA-ARS, Ft. Pierce research horticulturalist and geneticist Ed Stover. The presentation focused on the development of HLB-tolerant and HLB-resistant citrus scions. See the details below.

Citrus Greening and the USDA Scion Breeding Program

The USDA Scion Breeding Program has been working to find citrus varieties that are resistant or tolerant of citrus greening, or HLB, since citrus tree tolerance was observed in 2009. When the devastating disease was discovered in a south Florida citrus grove in 2005, it was believed that citrus greening would kill all citrus varieties. In 2010, the first crosses for HLB-tolerance were made.

Stover maintained there have been more than 26,000 unique hybrids produced in last 10 years, with 29 cultivars being released. Stover shared there are over 19,000 new hybrids in the ground and more in greenhouses.

Some of the highlighted scions include:

US SunDragon: It’s the first released scion containing Poncirus, or trifoliate orange, for use as fresh fruit. It’s described as “like a navel in alligator-hide,” has an apparent tolerance to HLB, and it scored highly in the sweet orange juice trial at USHRL.

FF 1-22-79, irradiated FF 1-42-65: A Fortune x Encore cross, Stover describes this as “Probably our best un-released tangerine.” It has good external and internal color, a slightly pebbly skin that usually comes off in large chunks with little chipping, and a very rich flavor, among other positive features.

Low seeded selections of Irradiated FF-5-51-2: A Clementine x Orlando cross, this is a “good midseason tangerine” that is easy peeling, has a rich flavor, and the segments are dry when separated. Its seedy original hybrid “appears to have useful HLB-tolerance, with no evidence of HLB-affected fruit.”

Citrus with a tolerance or resistance to citrus greening may soon be the norm rather than the exception.

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